Species: lammersorum DODSON, 1986
Etymology: In honor of the Lammers family of Shawmut, Montana, owners of the Careless Creek Ranching Company, and peerless hosts adn facilitators of our field work.
= Avaceratops lammersi DODSON, 1986

Holotype: ANSP 15800

Locality: Careless Creek, about 150 km northwest of Billings and 160 km south of the Leidy-Cope localities on the Missouri River, near Shawmut, Wheatland County, Montana.

Horizon: Judith River Formation.

Biostratigraphy:

Age: Judithian age, Campanian Stage, Senonian subepoch, Upper Gulf epoch, Late Cretaceous.

Material: Parietal, left squamosal, coossified basioccipital-exoccipital, left and right quadrates and quadratojugals, left jugal, left and right maxillae, left premaxilla, left and right pterygoids, and right dentary, first three coalesced cervicals, five posterior cervicals, six dorsals, one poorly preserved sacral centrum, two caudal centra and one caudal spine, fragmentary ribs, left scapula, coracoids, left humerus, left ulnae and radius, metacarpals II-IV, 10 phalanges, femora, tibiae and fibulae, and pes.

Skull.

Braincase.

A); Left splenial in internal view; B) Teeth; C) Dentary.

Left pterygoid in internal and external views.

Jugal.

Top) Maxilla; Bottom, Premaxilla.

A); Left quadrate in caudal view; B) Left quadratojugal in caudal view; C) external view; D)

Top view of frill.

A); Manus, B); Pes; C) Phalanges and ungual.

Humerus.

Ulna and radius.

A) Ungual in ventral, lateral and dorsal view; B) ?Right fibula; C) Right tibia; D) Right femur.

Scapula and coracoid.

Ribs.

Metatarsals.

A) Atlas/axis; B) Cervical vertebra; C) Neural arch.

A) Caudal vertebrae; B) Dorsal vertebrae.

Referred material:

PENKALSKI & DODSON, 1999

USNM 4802: An isolated left squamosal.

USNM 2415: Left squamosal. (= Ceratops sp in Hatcher, Marsh,& Lull, 1907)

 

HORNER, 1988

Locality: UCMP Locality No. V83125, Canadian Creek, Hill County, Montana.

Horizon: Judith River Formation.

Biostratigraphy:

Age: Judithian age, Campanian Stage, Senonian subepoch, Upper Gulf epoch, Late Cretaceous.

Material:

MOR: Partial skeleton.

 

PENKALSKI, 1994

Locality: About 125 km north-northeast of the type locality of Avaceratops, Careless Creek, about 150 km northwest of Billings and 160 km south of the Leidy-Cope localities on the Missouri River, near Shawmut, Wheatland County, Montana.

Horizon: Judith River Formation.

Biostratigraphy:

Age: Judithian age, Campanian Stage, Senonian subepoch, Upper Gulf epoch, Late Cretaceous.

Material:

MOR 692: Fragmentary skull.

Avaceratops lammersorum (modified from PENKALSKI, 1994), MOR 692.